It has been known that a direct methanol type fuel cell (DMFC) is suited for realizing equipment in a small size since it is capable of creating an electrochemical reaction by directly feeding methanol which is a fuel to the anode (fuel electrode) without using reformer for taking out hydrogen. Therefore, the direct methanol type fuel cell is drawing attention for use, particularly, with portable devices. Concerning such small fuel cells, use of metal materials has been proposed in an attempt to decrease the size of the cartridge and to make it possible to use under high-temperature conditions.
On the other hand, the direct methanol type fuel cell is of the nature in which methanol which is the fuel is directly fed to the anode to create the electrochemical reaction which, however, is impaired by metal ions present in the fuel methanol resulting in a decrease in the electromotive force and in a decrease in the generation capability. When treating the fuel such as methanol that is oxidized at the time of generating electricity and turns into an acidic oxide or treating the fuel cell using the fuel that tends to exhibit acidity, therefore, it is important that the metal material that comes in contact with the fuel does not elute out metal ions thereof.
To prevent elution of metal ions from the metal materials, in general, attempts have been made to treat the metal surfaces to become passive as disclosed in JP-A-2002-42827 and JP-A-2000-345363, to use an austenite type stainless steel having excellent corrosion resistance as disclosed in JP-A-2000-328200, to form a gold plating or a film of polytetrafluoromethylene, or to use titanium as a metal blank.